Arsenic removal from natural groundwater using 'green rust': Solid phase stability and contaminant fate

Jeffrey Paulo H Perez; Adrian Alexander Schiefler; Sandra Navaz Rubio; Markus Reischer; Niels Døssing Overheu; Liane G Benning; Dominique J Tobler

doi:10.1016/j.jhazmat.2020.123327

Arsenic removal from natural groundwater using 'green rust': Solid phase stability and contaminant fate

J Hazard Mater. 2021 Jan 5:401:123327. doi: 10.1016/j.jhazmat.2020.123327. Epub 2020 Jun 27.

Authors

Jeffrey Paulo H Perez¹, Adrian Alexander Schiefler², Sandra Navaz Rubio³, Markus Reischer⁴, Niels Døssing Overheu⁵, Liane G Benning³, Dominique J Tobler⁶

Affiliations

¹ GFZ German Research Center for Geosciences, Telegrafenberg, 14473 Potsdam, Germany; Department of Earth Sciences, Freie Universität Berlin, Malteserstr. 74-100, 12249 Berlin, Germany. Electronic address: jpperez@gfz-potsdam.de.
² Nano-Science Center, Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark; Capital Region of Denmark, Kongens Vænge 2, 3400 Hillerød, Denmark.
³ GFZ German Research Center for Geosciences, Telegrafenberg, 14473 Potsdam, Germany; Department of Earth Sciences, Freie Universität Berlin, Malteserstr. 74-100, 12249 Berlin, Germany.
⁴ Nano-Science Center, Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark; NIRAS A/S, Sortemosevej 19, 3450 Allerød, Denmark.
⁵ Capital Region of Denmark, Kongens Vænge 2, 3400 Hillerød, Denmark.
⁶ Nano-Science Center, Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.

PMID: 32645539
DOI: 10.1016/j.jhazmat.2020.123327

Abstract

Arsenic (As) contamination in groundwater remains a pressing global challenge. In this study, we evaluated the potential of green rust (GR), a redox-active iron phase frequently occurring in anoxic environments, to treat As contamination at a former wood preservation site. We performed long-term batch experiments by exposing synthetic GR sulfate (GR_SO4) to As-free and As-spiked (6 mg L^-1) natural groundwater at both 25 and 4 °C. At 25 °C, GR_SO4 was metastable in As-free groundwater and transformed to GR_CO3, and then fully to magnetite within 120 days; however, GR_SO4 stability increased 7-fold by lowering the temperature to 4 °C, and 8-fold by adding As to the groundwater at 25 °C. Highest GR_SO4 stability was observed when As was added to the groundwater at 4 °C. This stabilizing effect is explained by GR solubility being lowered by adsorbed As and/or lower temperatures, inhibiting partial GR dissolution required for transformation to GR_CO3, and ultimately to magnetite. Despite these mineral transformations, all added As was removed from As-spiked samples within 120 days at 25 °C, while uptake was 2 times slower at 4 °C. Overall, we have successfully documented that GR is an important mineral substrate for As immobilization in anoxic subsurface environments.

Keywords: Adsorption; Aging effects; Groundwater remediation; Iron (oxyhydr)oxides; Mineral stability.

Publication types

Research Support, Non-U.S. Gov't